The invention relates to a device for palleting slab-form products, especially book blocks or books.
With known devices of this type, there is first of all formed a series of a predetermined number of the products on a conveyor belt, and the series is thrust laterally onto a horizontally borne plate. This process is repeated until there is formed a so-called set of a certain number of adjacently arranged rows. The plate is disposed over a pallet which is raisable and lowerable with a corresponding arrangement. After completion of the set, the plate is drawn in along the set plane and parallel to the edge of the conveyor belt which is adjacent to the set position. By a stationary pressing, the products of the set are pushed from the plate, so that the products are deposited directly on the floor of the pallet or on the uppermost product layer for the formation of a stack in layers. Such a device is disclosed in German unexamined patent specification OS No. 27 18 338.
With such above device, it is possible, to be sure, to form stacks in which by previous turning, the slab-form products occupy different positions in individual rows. But it is not possible, as desired in many cases of utilization, to provide gaps or spaces between the product rows. With such spaces and with a composite stack, the stability of the stacked products on the pallet can be improved. In the stripping of a product layer from the plate, friction is generated between the products and the plate, which can impair the quality of sensitive products. Between the plate and the uppermost product layer on the pallet, there must be provided a sufficient vertical spacing so that the plate, when being withdrawn, does not come in contact with the products on the pallet so as to tear into and damage the stack. This vertical spacing, however, can impair the positionally accurate depositing of the products on the uppermost layer, because the products in the stripping thereof must overcome this height difference and can, in the process, slip uncontrolled so as to act upon the freestanding stack on the pallet in such a way that the uppermost products slip or the stack partly collapses.
A further disadvantage of such known device is that the pallet has to be lowered after such layer formation. This movement is not always free of jarring, so that it can occur that the already formed, relatively high free-standing stack, as a result of such jarrings, collapses entirely or in part.
Another, similar palleting device operates with a forward and back as well as an up-and-down stacking arm, such as disclosed in German unexamined patent specification OS No. 31 39 828, where the stacking arm can be driven into any desired position over a pallet. The stacking arm consists essentially of a horizontally arranged endless conveyer belt with upper and lower belt portions. A plate is arranged between the belt portions, with the plate being movable forward and back from the belt portions. On the conveyer belt, there is first of all formed a product row, possibly with spacings between the products. A pusher thrusts the product row laterally out from the conveyer belt onto the driven-out plate. The plate is disposed over the uppermost row of the pallet, onto which the product row from the plate is to be deposited. The plate is withdrawn with the pusher being at a standstill, so that the products are stripped off by the pusher.
With this latter known palleting device it is possible, to be sure, to stack one row on another row and with spacings between the stacked rows, where the spacings can be formed by the corresponding travel of the stacking arm over the pallet or by the corresponding travel of the pallet itself after the formation of the rows on the pallet. The stripping of the product row from the plate, however, can also bring about the disadvantages arising in the other device already described above, being brought about by the friction. Furthermore, in this latter case, too, the stripping can impair the positionally accurate depositing of the product row. Moreover, in each case, only one row and no entire set can be deposited on the pallet, which can decrease the palleting speed.
From the disclosure of German OS No. 30 24 133, there is known a conveying and/or stacking device, especially for individually light and easily deformable goods, such as for example, magazines. This device consists of a movable transport frame with a flat, overhanging carrying element forming a support surface, which can be drawn forth from under the deposited transport material, and which thereupon can be thrust back into the carrying position. The carrying element consists of two steel plates arranged one over the other, each plate being drawn over with a band, and each band being fastened to the machine frame. The band of the upper plate is firmly seated in the region of the upper belt side, and the band of the lower plate is firmly seated in the region of the lower belt side. In the withdrawal of the carrying element, it is achieved that the belts stand still, so that no relative movement takes place between the surface of the carrying element and the carried stack, as well as with respect to the stack on which the carried stack is to be deposited.
The latter known device makes it possible that the carrying element, before the withdrawing thereof, can be emplaced on the stack on which the carried stack is to be deposited, in which process there can also be generated a pressing or pushing of the lower stack. The layer-like formation of a stack is not directly offered by this known device, because it is difficult, during the traveling out of the carrying element, to arrange a product set or layer on the carrying element.